This thesis describes the implementation of thermally treated aluminum-doped zinc oxide (ZnO:Al) as front electrode (transparent conducting oxide, TCO) in thin-film silicon tandem solar cells based on amorphous silicon (a-Si:H) and microcrystalline silicon (µc-Si:H). In previous studies it was found that the opto-electronic properties of ZnO:Al (i.e. mobility) are fundamentally improved upon annealing at temperatures up to 650°C when capped with an a-Si:H layer. First of all, this process was scaled and technologically implemented in the solar cell development at PVcomB. Afterwards, this phenomenon was further investigated in a systematic study with focus on application in tandem solar cells. DC-sputtered ZnO:Al both from an industrial supplier and in-house developed have been used. Generally, two routes were identified: (1) Improving the transparence of the ZnO:Al while maintaining the thickness and sheet resistance and, (2), minimizing the TCO thickness, thereby, maintaining cell efficiency. The first approach led to tandem cells with highest conversion efficiency, reaching 12.1 % (after light soaking). Moreover, series connected mini modules with 11.6 % (after light soaking, apert. area) were demonstrated. The second approach first allowed to reduce the ZnO:Al layer thickness from 820 to 550 nm while maintaining efficiency. For thinner ZnO:Al layers micro-textured glass was used as substrate, since small ZnO:Al thickness did not allow to sufficiently texture the surface by etching. Light management in tandem solar cells based on such front electrode systems was investigated in detail. With this approach it was demonstrated in mini modules that an annealed ZnO:Al layer as thin as 100 nm did not result in significant efficiency loss compared to the reference.
|Advisor:||Rech, BerndStannowski, BerndRuske, Florian|
|School:||Technische Universitaet Berlin (Germany)|
|Source:||DAI-C 81/1(E), Dissertation Abstracts International|
|Subjects:||Materials science, Condensed matter physics|
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